Yksipisteruiskutusjärjestelmä

Yksipisteruiskutusjärjestelmä, often abbreviated as SPI, is a type of fuel injection system used in internal combustion engines. Unlike multi-point fuel injection (MPI) systems that deliver fuel to each cylinder individually, SPI systems use a single injector positioned in the intake manifold, close to the throttle body. This single injector sprays fuel into the incoming air stream, which is then distributed to the cylinders as the air-fuel mixture is drawn in.

The primary advantage of SPI systems is their simplicity and lower cost compared to more complex fuel injection systems. This made them a popular choice for entry-level and economy vehicles during the late 1980s and early 1990s. They offered improved fuel efficiency and emissions control over traditional carburetors while being less expensive to manufacture and maintain.

However, SPI systems have limitations. The distribution of the air-fuel mixture to individual cylinders can be less precise than with MPI, potentially leading to variations in performance and efficiency between cylinders. This can also result in less optimal combustion under certain engine operating conditions. As engine technology advanced and emissions regulations became stricter, SPI systems were largely replaced by more sophisticated MPI and direct injection (DI) systems. While no longer common in new vehicles, understanding SPI provides context for the evolution of fuel delivery technology.